Electric heat storage furnaces have been used for a number of years in Europe, where time-of-day electric power rate structures are utilized by the power companies as a means for managing peak power demands. These heat storage furnaces contain high heat capacity refractory bricks, typically composed of magnesite or olivine, which are electrically heated with resistance heating elements during off-peak hours when the electric power rates are lowest. During peak periods when electricity costs more, an air delivery system circulates air through the heated bricks, and delivers the heated air at the desired temperature as required.
Due to the increasing peak power demands on domestic utility companies and the high cost of building additional generating capacity, time-of-day power rate structures of the type already in use in Europe have begun to receive favorable consideration in the United States. The introduction of this type of rate structure will make it economically desirable to use the above-noted type of heat storage furnace for residential, commercial and industrial heating.
Because of its high heat capacity and relatively low cost, olivine, a magnesium-iron-orthosilicate mineral, has been widely used in producing the heat storage bricks used in English and German heat storage furnaces. The olivine for use in these bricks comes principally from deposits located in Norway, Sweden, and Austria. However, because of the weight and fragile nature of these European heat storage bricks, it is impractical and economically unfeasible to import such bricks for use in the U.S. market.
The United States has extensive deposits of olivine in western North Carolina, northern Georgia, and in the State of Washington. Olivine from these deposits differs somewhat compositionally from the olivine found in European deposits and heretofore has been utilized principally for refractories, foundry sand, blasting sand and as a fluxing agent in blast furnaces. Olivine from domestic deposits has not heretofore been used for heat storage applications.
With the foregoing in mind, it is a primary objective of the present invention to produce from domestic rather than imported olivine, an olivine refractory brick having thermal and physical properties suited for heat storage furnace applications.
It is a further objective of this invention to produce such products economically from domestic raw materials by processes which are compatible with domestic ceramic industrial practices, and having optimal physical and thermal properties which are consistent with domestic utilization of off-peak energy storage technology. In this regard, it should be understood that existing differences in lifestyles, climates, housing designs and construction methods, as well as differences in relative costs of various energy forms and relative availability of investment capital between the United States and Europe will dictate the development of differently sized, controlled and optimized heat storage furnaces for the United States market, and consequently the optimal ceramic refractories for such domestic heat storage furnaces may need to be technically different from their older European counterparts.